1. Field of the Invention
The present invention relates to a vehicle roof rack formed by coating a core member with synthetic resin using an insert molding technique.
2. Description of Related Art
One type of roof rack installed on top of the roof of passenger cars and other vehicles is often manufactured by an insert molding process. In this process the metal core member of the roof rack is placed in the mold at a specific position and molten resin is then injected to fill the mold cavity and coat at least a specific surface area of the core member with synthetic resin.
By manufacturing the roof rack in this way, the strength and rigidity required in a roof rack is assured by the metal core member while coating all or a particular area of the surface of the core member with synthetic resin reduces the overall weight and improves the appearance of the roof rack. Insert molding also results in an integral molding of the coating resin and core, thereby helping to reduce the number of parts in the complete roof rack assembly, eliminating an additional step of assembling the coating and core, and improving adhesion between the coating and core.
The applicant previously invented a method for inserting and securing the core in the mold during insert molding of this type of roof rack. More specifically, the method the applicant disclosed in Japanese Patent Laid-Open Publication HEI 10-129359 applies to a roof rack assembly in which the core of the rack rail extending longitudinally to the vehicle, and the core of the support bracket for mounting the rail to the vehicle roof, are made of metal. The support bracket cores and the rack rail core are first fastened together, and the support bracket cores are then placed in the mold at a specific position using an intervening insert. The complete core assembly is thus inserted to and secured inside the mold.
Changes in owner preferences and aesthetics have led to various changes in vehicle design and appearance. Not only have these changes affected the roof rack installed on the vehicle roof top, they have also made the structure for installing the roof rack more complex in the pursuit of a vehicle that looks better even with a roof rack installed.
One stylistic change in car design has been to rounded edges and a rounded roof. Installing a roof rack on a rounded roof has meant that the support brackets must be offset noticeably to the outside or inside from the conventional position directly vertically below the rack rail. As shown in FIG. 40 to FIG. 42, this requires a bend in the support bracket metal cores 230, 240, 250 at some point along the vertical axis thereof. The top of each support bracket metal core 230, 240, 250 is then joined with a pipe-shaped rail core 220, thus assembling core member 210 so that the mounting bolt 208 affixed to the bottom of each support bracket metal core 230, 240, 250 is positioned to the outside, for example, of the axis of the pipe-shaped rail core 220 of the roof rack.
A problem with this design is that because of the high precision required when bending and forming the support bracket metal cores 230, 240, 250, production is time-consuming and it is quite difficult to maintain the required shape and dimensional precision.
It should be noted that the support bracket metal cores 230, 240, 250 could be formed in the shape of closed boxes so that molten resin is prevented from filling the inside of the box and the box thus stays hollow. This reduces the amount of resin used and keeps the weight down. The problem with this technique is that it is even more difficult and relatively expensive to produce such box-like metal core members. It is particularly difficult to form the metal core members as closed boxes when a bend is required as described above, and it is therefore difficult in practice to prevent resin from filling the core members and thus keep weight down by controlling the resin amount.
The roof rack rails are also long and relatively slender with the length significantly long in relation to the cross sectional area. It is therefore standard practice to use three support brackets, referred to as the front, center, and rear supports, on each rail. Due to vehicle design considerations, however, the center support is often noticeably offset from the actual center, typically toward the rear support, for example.
The resulting long span between the front support and the center support means that the distance between the fixed points at which the pipe-shaped core 220 is supported is also long. As a result, when molten resin Rxe2x80x2 is injected during the insert molding process, resin pressure can cause the long unsupported length of pipe-shaped core 220 between front and center supports to bend and shift in position.
Because it is very difficult to inject and fill resin Rxe2x80x2 evenly throughout the mold cavity, forcibly injecting resin to the mold cavity results in an uneven distribution of resin pressure, thus causing the position of pipe-shaped core 220 to shift and the thickness of coated resin layer Rxe2x80x2 to become uneven. There are also adverse effects on the bond between coating resin Rxe2x80x2 and the surfaces of core members 210, 230, 250. Adhesion to the core member 210 is particularly low where coating resin Rxe2x80x2 thickness is thin, and appearance defects such as blistering can occur easily.
It should also be noted that roof rack rails are installed in pairs. Manufacturing would therefore be much more efficient and molding easier if the roof rack rail assemblies could be molded in pairs at the same time in the same mold (using multipart molding). The problem with molding two components in a single mold assembly is that using plural gates to supply resin for each molding (roof rack) complicates mold design and makes it more difficult to control molding conditions.
It would therefore be convenient if a single gate common to both die units could be provided between two parallel roof rack mold sections to supply molten resin simultaneously from this one gate to the pair of roof rack molds.
As will be well understood from FIGS. 41 and 42, however, a hood-shaped coating resin layer Rxe2x80x2 is formed covering the top of pipe-shaped core 220 in roof rack 201 and descending therefrom to both sides. The distance from the bottom on the right side of coating resin layer Rxe2x80x2 up and over the top and back down to the bottom on the left side is thus very long in the direction through the vertical section perpendicular to the long axis of pipe-shaped core 220. Furthermore, when resin is supplied from only one side of the mold using a single gate and the thickness of coating resin layer Rxe2x80x2 is limited to some maximum thickness in order to minimize weight, it is difficult to assure that the molten resin completely fills the mold cavity all the way to the lower end of the resin layer at the farthest point from the runner extend from the gate.
Furthermore, ribs 288 are desirably added to the support brackets for reinforcement due to the length of the roof rack 201 itself and the limited thickness of the coating resin layer Rxe2x80x2 forming the outside walls of the finished molding (roof rack 201). However, if these ribs 288 exceed a particular thickness, appearance defects known as sink marks can occur easily on the surface where the ribs 288 join the coating resin layer Rxe2x80x2. It is therefore necessary to limit the thickness of the ribs 288.
However, if the ribs are too thin, a drop in molten resin filling characteristics in the area of the ribs during injection molding means that tall ribs (ribs with a large surface area) cannot be formed. In practice this means that ribs cannot be formed to the full height of the roof rack 201, and are thus limited in height as indicated by the double-dot dash lines in FIGS. 41 and 42. The problem with such low ribs 288 is that they cannot provide sufficient reinforcement for the coating resin layer Rxe2x80x2 (outer walls of the product).
The present invention was conceived with respect to the aforementioned problems, and an object of the invention is to provide a vehicle roof rack manufactured by insert molding such that manufacturing and controlling the precision of the support bracket core are simple and appearance defects can not easily occur, and resin can be supplied to the insert mold from only one side, or ribs that can provide solid reinforcement can be formed.
To achieve this object, a vehicle roof rack according to the present invention has a vehicle mounting bracket and a rack rail extending longitudinally to the vehicle body on top of the vehicle roof, the roof rack being formed by placing a core in a specific location inside a mold cavity and injecting molten resin to the mold cavity to form a synthetic resin coating on at least a specific surface area of the core. The core of this roof rack includes a rail core as the core of the rack rail, and a support bracket core as the core of the mounting bracket. The support bracket core is integrally molded from synthetic resin to include a mechanism for fastening the support bracket core to the rail core and a mechanism for fastening the roof rack to the vehicle.
By manufacturing the support bracket core, which is the core of the roof rack support bracket, from synthetic resin, the support bracket cores can be manufactured in large volume with uniform quality using a molding process whereby a molding die is filled with molten resin. Compared with conventional bending and shaping of a metal member, production is significantly better, and it is easier to maintain shape and dimensional precision.
Furthermore, because the mechanism for fastening the support bracket core to the rail core and the mechanism for fastening the roof rack to the vehicle are integrally molded together, the structure of the support bracket core can be simplified and productivity can be further improved.
Yet further, adhesion of the resin coating is also greatly improved compared with a conventional metal support. As a result, separation of the resin coating from the support core surface is more difficult even when the resin coating is thin, and appearance defects such as blistering of the resin coating can be suppressed.
Preferably, the mechanism for fastening the support bracket core to the rail core is a through-hole through which a threaded member is passed to fasten the support bracket core to the rail core, and the mechanism for fastening the roof rack to the vehicle is a bolt having a threaded shaft protruding from a support bracket core base bottom that is fastened to the vehicle.
When the mechanism formed in the support bracket core for fastening the support bracket core to the rail core is a through-hole through which a threaded member such as a screw can be passed to fasten the support bracket core to the rail core, it is yet further possible to easily and reliably fasten the support bracket core and the rail core together using a simple screw.
Furthermore, by using an embedded bolt of which the threaded shaft protrudes from the bottom of the support bracket core base fastened to the vehicle as the mechanism for attaching the roof rack to the vehicle, the support bracket core and roof rack can be easily and reliably attached to the vehicle by simply threading and tightening a nut onto the exposed bolt threads.
Further preferably, a recess is formed to a specific depth from a specific bottom reference surface of the support bracket core so that this recess is connected to the resin supply runner of the molding die, and said through-hole is formed in a inside wall of the recess.
In this case, further preferably, the through-hole for the threaded member is provided through the bottom wall of a recess of a specific depth from a specific bottom reference surface of the support bracket core. This makes it simple to insert and tighten the threaded member from the recess.
In addition, because this recess also communicates with the resin supply runner of the mold, the recess can be easily filled with resin when the support bracket core and rail core are fastened together by the threaded member and the coating resin is then supplied to and fills the mold cavity. The head of the threaded member is also covered by the filler resin, thus preventing corrosion of the threaded member and preventing the threaded member from loosening due to vehicle vibration.
Yet further preferably, the support bracket core is held in the mold using an insert, and a resin path is also formed in part where the support bracket core and insert contact. This resin path connects end parts of a mold cavity nearest and farthest from the resin supply runner when seen in vertical section perpendicular to the longitudinal axis of the rail core, and the mold cavity is formed between an outside surface of the support bracket core and an inside surface of the molding die.
In this case, yet further preferably, the support bracket core is held in the molding die using an insert. The force required to secure the long rail core thus does not act directly on the rail core, and the resulting deflection and deformation of the rail core can thus be prevented.
When seen in vertical section perpendicular to the longitudinal axis of the rail core, a resin path connecting the near and far end parts of the mold cavity, which is formed between the outside surface of the support bracket core and the inside surface of the molding die, from the resin supply runner is also formed in part where the support bracket core and insert contact. It is therefore possible to assure that the molten resin flows relatively easily and reliably through this resin path to the far side of the mold cavity from the resin supply runner. This means that the resin supply gate can be is provided on only one side of the support bracket core while still assuring that the molten resin flows reliably from the gate throughout the mold cavity, including to the end farthest from the gate.
A vehicle roof rack according to another version of the invention has a vehicle mounting bracket and a rack rail extending longitudinally to the vehicle body on top of the vehicle roof, the roof rack being formed by placing a core in a specific location inside a mold cavity and injecting molten resin to the mold cavity to form a synthetic resin coating on at least a specific surface area of the core. The core includes a rail core as the core of the rack rail, and a support bracket core made of synthetic resin as the core of the mounting bracket, and has a plurality of ribs disposed integrally thereto connecting the support bracket core body and the resin coating formed as the outside cover of the roof rack. The mold cavity part corresponding to the ribs as seen in vertical section perpendicular to the longitudinal axis of the rail core communicates with the resin supply runner part of the molding die.
By manufacturing the support bracket core, which is the core of the roof rack support bracket, from synthetic resin, the support bracket cores can be manufactured in large volume with uniform quality using a molding process whereby a molding die is filled with molten resin. Compared with conventional bending and shaping of a metal member, production is significantly better, and it is easier to maintain shape and dimensional precision.
A plurality of ribs connecting the resin coating functioning as the outside wall of the roof rack, and the body of the support bracket core, is further preferably provided. These ribs assure the strength and rigidity required in the roof rack while keeping the support bracket core compact and lightweight. This means that a lightweight roof rack can also be achieved.
The mold cavity corresponding to these ribs when seen in vertical section perpendicular to the longitudinal axis of the rail core is also connected to the resin supply runner of the molding die. This makes it possible to supply and fill the mold cavity with molten resin from this part during insert molding, assure sufficient bond strength between the ribs and outside wall of the roof rack, and thus increase the strength and rigidity of the support bracket.
Preferably in this case the ribs are formed integrally to and projecting out from the support bracket core body.
The thickness of the ribs also has no effect on the appearance of the outside of the roof rack because the ribs project from the body of the support bracket core and are formed integrally to the support bracket core body. That is, even if rib thickness is increased for reinforcement to improve the rigidity and strength of the outside wall of the roof rack, sink marks or other visual defects will not form in the roof rack wall area connected to the ribs as a result of increased rib thickness, and appearance will therefore not be degraded.
Other objects and attainments together with a fuller understanding of the invention will become apparent and appreciated by referring to the following description and claims taken in conjunction with the accompanying drawings.